1. Field of the Invention
This invention relates to surfaces which absorb photons having wavelengths on the order of the wavelength of visible light. This invention also relates to the production of such surfaces by the directional solidification of eutectic compositions and the subsequent selective removal of one of the eutectic phases.
2. Description of the Prior Art
U.S. Pat. No. 4,005,698 describes a photon energy converter which consists of a surface having protruding tungsten dendrites. These dendrites do not extend into the substrate and are produced by the reduction of gaseous tungsten hexafluoride. Theinventors of this patent also authored an article entitled "A New Concept For Solar Energy Thermal Conversion" in Applied Physics Letters, Vol. 26, No. 10, May 15, 1975, pages 557-559.
In a different subject area, but one which relates to this invention, it is known that under certain solidification conditions, an oriented microstructure may be produced in a eutectic composition. This is taught in U.S. Pat. Nos. 3,124,452; 3,528,808; 3,552,953; 3,554,817; 3,564,940 and 3,671,223, all of which are assigned to the assignee of the present invention.